			Home About us Contact

Strain Development (strain + development)

Distribution by Scientific Domains

Life Sciences	50%

Selected Abstracts

Gluconic acid production by Aspergillus terreus

LETTERS IN APPLIED MICROBIOLOGY, Issue 3 2010
C. Dowdells
Abstract Aim:,Aspergillus terreus produces itaconic acid at low pH but lovastatin and other secondary metabolites at higher pH in the fermentation. The utilization of glucose as a carbon substrate was investigated for secondary metabolite production by A. terreus. Methods and Results:, With a starting pH of 6·5, glucose was rapidly metabolized to gluconic acid by the wild-type strain and by transformants harbouring Aspergillus niger genes encoding 6-phosphofructo-1-kinases with superior kinetic and regulatory properties for bioproduction of metabolites from glucose. On exhaustion of the glucose in batch fermentations, the accumulated gluconic acid was utilized as a carbon source. Conclusions:, A novel pathway of glucose catabolism was demonstrated in A. terreus, a species whose wild type is, without any strain development, capable of producing gluconic acid at high molar conversion efficiency (up to 0·7 mol mol,1 glucose consumed). Significance and Impact of the Study:,Aspergillus terreus is a potential novel producer organism for gluconic acid, a compound with many uses as a bulk chemical. With a new knowledge of glucose catabolism by A. terreus, fermentation strategies for secondary metabolite production can be devised with glucose feeding using feedback regulation by pH. [source]

In situ monitoring of residual strain development during composite cure

POLYMER COMPOSITES, Issue 3 2002
Allan S. Crasto
Internal (residual) stresses build up in a thermosetting composite as the matrix shrinks during cure, and again as the composite is cooled to ambient from its elevated processing temperature. These stresses can be significant enough to distort the dimensions and shape of a cured part as well as initiate damage in off-axis plies, either during fabrication or under the application of relatively low mechanical loads. The magnitude of these stresses depends on a number of factors including constituent anisotropy, volume fraction and thermal expansion, ply orientation, process cycle, and matrix cure chemistry. In this study, embedded strain gauges were employed to follow, in situ, the buildup of residual strains in carbon fiber-reinforced laminates during cure. The data were compared to those from volumetric dilatometer studies to ascertain the fraction of resin shrinkage that contributed to residual stress buildup during cure. Based on earlier studies with single-fiber model composites, the process cycle in each case was then varied to determine if the cycles optimized to minimize residual stresses for isolated fibers in an infinite matrix were applicable to the reduction of residual stresses in conventional multifiber composites. The results of these studies are reported here. [source]

Microalgae for the production of bulk chemicals and biofuels

BIOFUELS, BIOPRODUCTS AND BIOREFINING, Issue 3 2010
Rene H Wijffels
Abstract The feasibility of microalgae production for biodiesel was discussed. Although algae are not yet produced at large scale for bulk applications, there are opportunities to develop this process in a sustainable way. It remains unlikely, however, that the process will be developed for biodiesel as the only end product from microalgae. In order to develop a more sustainable and economically feasible process, all biomass components (e.g. proteins, lipids, carbohydrates) should be used and therefore biorefining of microalgae is very important for the selective separation and use of the functional biomass components. If biorefining of microalgae is applied, lipids should be fractionated into lipids for biodiesel, lipids as a feedstock for the chemical industry and ,-3 fatty acids, proteins and carbohydrates for food, feed and bulk chemicals, and the oxygen produced should be recovered also. If, in addition, production of algae is done on residual nutrient feedstocks and CO2, and production of microalgae is done on a large scale against low production costs, production of bulk chemicals and fuels from microalgae will become economically feasible. In order to obtain that, a number of bottlenecks need to be removed and a multidisciplinary approach in which systems biology, metabolic modeling, strain development, photobioreactor design and operation, scale-up, biorefining, integrated production chain, and the whole system design (including logistics) should be addressed. Copyright © 2010 Society of Chemical Industry and John Wiley & Sons, Ltd [source]

Optimized evolution in the cytostat: A Monte Carlo simulation

BIOTECHNOLOGY & BIOENGINEERING, Issue 1 2009
Alan Gilbert
Abstract Rational genetic alterations of a microorganism for a specific purpose are not possible in many situations where our knowledge of the relationship between phenotype and genotype is limited. In such cases evolutionary techniques must be applied. Evolutionary methods are usually time consuming; therefore, more efficient techniques are highly desirable. In this work we present the optimization of strain development in a cytostat. The time required for mutant strain isolation is dependent on the total cells present, the wild-type specific growth rate, the beneficial mutation probability, the mutant specific growth rate, and several bioreactor operating conditions. These parameters are highly related, and a theoretical model, as developed here, is needed to define the conditions that optimize the isolation. The model is based on a discrete, stochastic description of mutant formation and selection in the background of abundant wild-type cells. Using the model, we determined the optimal cytostat operating strategy for mutant isolation that varies according to the probability of beneficial mutations. It is also shown that mutants with as little as a 5% growth advantage can be isolated in less than 15 days which is significantly faster than in a chemostat. The described optimal mutant isolation procedure is expected to be particularly useful for the generation of industrial strains that are robust in challenging growth conditions. Biotechnol. Bioeng. 2009;102: 221,231. © 2008 Wiley Periodicals, Inc. [source]